This invention relates to devices for applying fluid to biological tissue and more particularly to apparatus which instills an aqueous solution into the eye. The invention has application, for example, as an unobtrusive and automatic device for introducing artificial tear fluid to relieve the discomfort and potential ocular damage caused by chronic dry eye condition, i.e., lachrymal deficiency. The invention also provides a corresponding method.
Many people suffer from a lack of eye moisture, resulting in discomfort and ocular damage. Even though available artificial tear solutions increase eye moisture and relieve discomfort, the application of an artificial tear solution provides only temporary relief. As a result, dry eye sufferers commonly apply artificial tear solution to their eyes repeatedly within the span of a day. The burden and interruption caused by frequent application of eye drops is a disincentive to applying the required dosages and to maintaining the proper moisture levels.
In addition to treating lachrymal deficiency, there is need for a device that introduces fluid into an eye to administer therapeutic agents that treat conditions such as corneal ulcerations. In these cases, an active medicinal agent is dissolved into a volume of fluid and administered to the eye. The applied fluid washes over the outer surface of the eye and thereby distributes the agent across the corneal surface. Introducing fluids having active medical ingredients to an eye requires careful control of the quantity of fluid administered. It generally is difficult, with the manual application of the fluid with an eye dropper, to control the number of drops introduced to the eye.
Some eye droppers exist that have a fluid chamber with a threaded piston that screws within a correspondingly threaded cylinder. The piston can be advanced within the cylinder by a selected number of threads and then held in position. By advancing the piston a pre-determined amount, a corresponding predetermined volume of fluid is expelled from the chamber. Due to the mechanics involved, these devices are usually bulkier and more cumbersome than typical eyedroppers. This unwieldliness adds to the disincentive of a patient to apply a fluid.
Other devices have been developed that deliver fluid to an eye. These devices typically work by pumping fluid from a reservoir through a tube that has its distal end positioned adjacent to the eye. In some applications, the tube is surgically implanted under the skin; it begins at a fluid reservoir positioned, for example, at the lumbar region and ends adjacent the eye. These devices are cumbersome and invasive, and the mechanism needed to pump the fluid through the length of the tube is bulky and requires a heavy and bulky power source. Furthermore, control problems result from having to pump fluid to the eye through the relatively lengthy tube. Also, fluid flow within the tube can be disrupted by patient movement, and by inadvertent pinching or collapsing of the tube.
Portable eye irrigation systems have been developed which require the user to carry relatively cumbersome pump equipment and which offer limited flexibility and comfort. "Mechanical Devices", The Preocular Tear Film and Dry Eye Syndromes, Spring 1973, Vol 13, No. 1, describes several such devices. Typically, the prior systems have a single fluid outlet disposed in contact with each eye. Some systems have controls that provide adjustment to the delivered fluid volume, and some systems provide continuous irrigation.
Therefore, it is an object of this invention to provide apparatus which administers fluid to the eye in a controlled and compact fashion. An apparatus according to this object can offer a user comfort while delivering droplets or therapeutic mist to the eye.
It is another object of the present invention to provide an apparatus that is convenient to use for the sustained introduction of fluid into a person's eye.
It is a further object of the invention to provide an apparatus which provides relatively precise control over the quantity and frequency of fluid administered into an eye.
Another object of this invention is to provide an apparatus for introducing fluid into an eye and that is non-invasive and visually non-obstructive.
A further object of this invention is to provide an apparatus for introducing fluid into an eye with relatively low impact of fluid on the corneal surface of the eye.
Yet another object of this invention is to provide a facile method and apparatus for introducing fluid and therapeutic agents into an eye.
Other objects of the invention will be apparent from the description that follows.